Cook's Holly

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Cook's Holly

Ilex cookii

ListedJune 16, 1987
FamilyAquifoliaceae (Holly)
DescriptionDwarf evergreen shrub with white flowers.
HabitatElfin, montane forests at high elevations.
ThreatsDeforestation, construction of roads and communications facilities.
RangePuerto Rico


Cook's holly, Ilex cookii, is an evergreen shrub or small shrub reaching 8 ft (2.4) in height. The leaves are alternate, simple, thin but leathery, glabrous, and entire. They are from 0.75-1.75 in (1.9-4.4 cm) long and 0.37-0.87 in (0.9-2.2 cm) wide and reach an abrupt point at the apex. The upper surface is dark shiny green and the lower a pale green with microscopic black dots.

Cook's holly is dioecious: male and female flowers are borne on different plants. Female flowers are minute and white. Fruits are a drupe. Male flowers have not been observed. Pollination is probably effected by insects or wind, although the pollination biology of this species has not been studied. Male flowers and ripe fruit have never been observed and at present only one mature individual is known. The remaining plants are small, both sprouts or seedlings, suggesting that root sprouting or re-sprouting may occur and that viable seed is occasionally produced.


The habitat of Cook's holly is elfin, montane forests at high elevations.


Cook's holly is found near the summits of Cerro Punta and Monte Jayuya, both within the Toro Negro Commonwealth Forest. By the turn of the twenty-first century it had not been reported from other sites. At the Cerro Punta location, there were only one mature individual and four sprouts of Cook's holly. At the Monte Jayuya location, the largest population consisted of about 30 sprouts or seedlings that were scattered along the ridgetops. The elevation at these sites ranged from 3,900-4,260 ft (1,188.7-1,298.4 m).


A serious threat to the dioecious species is the effect population numbers may have on successful reproduction. Only one mature individual is known to exist, and neither male flowers nor mature fruit of this species have ever been reported. Regular pollination and viable seed production may rarely occur and recruitment may be too low to maintain or increase population numbers. Therefore, unless there are sufficient numbers of undiscovered plants, the species could eventually become extinct.

Conservation and Recovery

The successful introduction of Cook's holly is dependent on the propagation of both male and female plants and on the production of viable seed.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345


Ayensu, E. S., and R. A. DeFilipps. 1978. Endangered and Threatened Plants of the Unites States. Smithsonian Institution and World Wildlife Fund, Washington, D. C.

Howard, R. A. 1968. "The Ecology of an Elfin Forest in Puerto Rico." Journal of Arnold Arboretum 49 (4): 381-418.

Proctor, G. R. 1986. Ferns of Puerto Rico and the Virgin Islands. New York Botanical Garden, Bronx.